The present invention relates to power production systems of the type which combine chemically reactive materials in a vessel or boiler/reaction chamber to produce heat energy substantially without evolution of exhaust gasses. More particularly, the present invention relates to apparatus of the described character wherein the chemical reaction may readily be controlled or throttled so that the rate of power production may be rapidly both increased and decreased between upper and lower levels. Still more particularly, the present invention relates to method of control and operation of power plant apparatus of the described type particularly directed to obtaining both rapid response to a command for a changed power output level as well as high efficiency of operation.
The desirability of utilizing combinations of highly exothermically reactive chemical compounds to produce mechanical power without the evolution of exhaust gasses has long been recognized. By way of example, U.S. Pat. No. 1,349,969, issued Aug. 17, 1920 to W. G. Leathers describes a closed power production system utilizing thermite as the chemical power source. However, the invention of Leathers recognizes the difficulty of controlling the reaction rate of the chemical compound. Leathers seeks to allow the chemical reaction to proceed unchecked and to control the power output of the system by holding the heat energy in a controllably insulated mass. However, such a system incurs many operating difficulties and low efficiency.
Another more recent example of related technology is seen in the U.S. Pat. No. 2,484,221 issued June 25, 1946 to E. A. Gulbransen wherein magnesium salt cake is reacted with water, hydrochloric acid, and hydrogen peroxide to produce steam for driving an expanding motor. The patent to Gulbransen gives only superficial attention to control of the rate of energy production of the system. No consideration is given to obtaining rapid response transients to a command for a changed power output level.
Still another recent example of the pertinent technology is seen in U.S. Pat. No. 3,486,332, issued Dec. 30, 1969 to A. E. Robertson, et al. In the invention of Robertson et al, lithium fuel contained in a boiler/reaction chamber is combined with a reactant such as bromine pentaflouride, or sulfur hexaflouride. Only two control functions are contemplated by the Robertson et al invention. One control regulates the rate of reactant supply to the reaction chamber to maintain a selected reaction temperature. The other control regulates the rate of feed water supply to control steam pressure at a selected level. From all appearances, the Robertson et al invention contemplates steady state operation of the power system after its start-up. No provision is made either for obtaining variable power output or rapid transient response to a command for a changed level of power output. With this type of control scheme the temperature of steam supplied to the turbine is directly related to reaction chamber temperature and inversely related to feed water flow rate. Consequently, were such a system to be throttled to a low level of power production, the low water flow rate would result in excessively high steam temperature to the turbine. In order to prevent such excessive steam temperature, the temperature of the reaction chamber must be lowered. Such lowering of the reaction chamber temperature incurs undesirable consequences in the chemical reaction of the metal fuel and reactant. Also, an undesirable result is that reaction chamber temperature must generally track the power output level of the plant. The reaction chamber has considerable thermal inertia so that power output changes will necessarily lag considerably behind a command for a changed power output level.
Yet another example of conventional teaching in the relevant technology is presented by U.S. Pat. No. 3,964,416 issued June 22, 1976 to R. J. Kiraly et al. In the invention of Kiraly et al, lithium fuel is reacted with sulfur hexafluoride. Once again, as in the invention of Robertson et al, the Kiraly et al invention contemplates only two controls on the reaction system. Throttling of the reaction rate, and rapid transient response to a request for changed power output are not addressed by the Kiraly et al invention.
Two more recent U.S. patents (in terms of patent application filing date) in the relevant technology recognize, at least implicitly, some of the problems with control of the chemical reactions of interest. U.S. Pat. Nos. 3,662,740, and 3,697,239, issued May 16, 1972, and Oct. 10, 1972 to J. Schroder contemplate a heat exchanger/reaction chamber wherein a pump is utilized to move reaction products from the reaction chamber to a settling chamber. In this way the metal salts resulting from the reaction will allegedly not crust on the cooler heat transfer surfaces. However, no provision for throttling or for obtaining rapid response of the chemical reaction system to a command for a changed power output level is contemplated by the Schroder patents.